1. Field of the Invention
This invention relates to devices known as inlet particle separators that remove sand and extraneous matter from air entering gas turbine engines and more particularly to improved flowpath contours for inlet particle separators.
2. Background of the Prior Art
Aircraft gas turbine engines are highly susceptible to damage from foreign objects introduced into air inlets of such engines. The problem has been most acute in the past with respect to relatively large foreign objects, such as stones, gravel, birds, and hail.
With the advent of gas turbine-powered helicopters and other verticle takeoff and landing (VTOL) aircraft, smaller particles of foreign matter, such as sand and ice, have become increasingly troublesome due primarily to the conditions under which such VTOL aircraft are frequently operated. The advantage of VTOL capability makes such aircraft particularly useful in areas where conventional air fields do not exist, frequently occurring in uninhabited and isolated areas. VTOL aircraft are also specially suited for certain low-altitude missions over both land and sea.
Under these and other similar conditions, substantial quantities of small foreign objects, such as sand and ice, may become entrained in intake air supplied to the gas turbine engine. These foreign particles, which individually have relatively little effect on the engine, can cause very substantial damage when ingested into the engine in large quantities. As an example, recent experience has shown that engines in helicopters operating at low altitude in a desert environment can lose performance very rapidly due to erosion of the engine blading by the ingestion of dust and sand particles. Similar problems can occur when operating over salt water because of heavy ingestion of salt water droplets which can cause both corrosion and destructive erosion of turbine structures.
In attempting to solve this problem, various inlet particle separator systems have been developed for use with different kinds of gas turbine engines. As one might expect, continuing development has led to improvements and more effective separation systems. While some of these systems are highly effective at removing extraneous matter, they often involve drawbacks in terms of detrimental effects on engine performance.
One means of providing highly effective separation is to mount a blower system with an engine inlet that centrifuges the inlet air entrained with particles before the air enters the engine core. Once the air is accelerated to a high centrifugal velocity with the particles entrained therein, relatively clean air can be drawn from an inner portion of the centrifugal flow into the core engine itself. Because of its density, the extraneous matter itself cannot be drawn radially inwardly as quickly as the air and instead the particles will tend to follow their original trajectory around an outer radius into a collection chamber.
While this system efficiently separates extraneous matter, there can be certain disadvantages associated with the blower system and there can be performance disadvantages from powering the blower itself.
It is, therefore, an object of the present invention to provide an inlet particle separator flowpath that does not require centrifugal acceleration of engine inlet air in order to separate extraneous matter.
It is another object of the present invention to provide an improved engine inlet particle separator that efficiently separates extraneous matter without using large amounts of engine power in a blower system.
It is another object of the present invention to provide an inlet particle separator that efficiently and effectively separates extraneous matter from engine inlet air with a system that does not draw the bulk of the extraneous matter through a blower thereby avoiding problems of blower deterioration.